So you need to archive data for years (if not decades), and you really don’t trust a service provider to both stay in business, and play fair, for that long a time frame.
A script that will use multiple, publicly available RFC 3161-compatible services for timestamping files.
A script that will monitor archive directories on a btrfs file system for changes, and call a user-defined bash function with a list of changed files and directories.
So, you are the IT department in charge of your home office backups. Let’s implement secure backups, and a time machine for home office Linux users.